Some good suggestions throughout this thread. I agree with the marquee signing being a midfielder this summer, as we possibly won't need reinforcements in attack anymore. But, do we really need a massive signing - should we not just go for an off the radar type of player; the type of signings SAF used to go for. These are my suggestions for the Summer:
Attacking Play.
Ozil : He's out of contract in the summer and will add to our creativity, can't hurt to ask can it. We lack this creativity without Pogba, Ozil can fill that place when he isn't available, the final pass is clearly still an issue as we saw in the game against Burnley last weekend.
Ji-Sung Park Type Player : Someone who turns up in big games, can provide the extra spark in the attack and provides the edge in those types of games.
Midfielder.
Any big signing that could play behind Pogba - give him even more freedom somewhat like Matic has so far. Pogba ahead of 2 midfielders in a 4-3-3 system is were I believe he plays his best football.
Defence.
At times this season we have been a mess in the back, but have also conceded the least amount of goals of any team in the Premier League this season, so somehow it's working. Lindelof will progress, hopefully and even possibly form a Formidable partnership with Bailly. Smalling and Jones both coming along this season but both are making too many mistakes, as good as they have been at times. Rojo, reminds me of Vidic at times, he's not afraid of anything, just needs to come back into action.
Need a replacement for Valencia though, as good as he has been these past two seasons, he's 33 next season - we should possibly bring in a young player to develop as Valencia fades. Looks like Mou is starting to like Shaw as well, who should continue to develop as Young fades, and hopefully finally fulfil the potential he has.